I had my only brief panic attack when scuba diving in Guam a few years back. It was only brief and minor, and after a brief re-surface I was OK and able to go back down. But I know how scary it felt. I can barely even imagine a major attack and how you must feel.
I really wish that we could still visit the cockpit while the plane is in flight. Some years ago before 9/11, I used to visit the cockpit and sometimes even spend up to atwo hours in there with them on long-haul flights between Asia or Europe and SFO. I really do think that may help but its now impossible. On the other hand, I would certainly recommend going up in a small plane, with a trusted pilot or instructor who will let you handle the controls. I will say that it will probably make you panic, at first, but so long as it is a nice calm day, and your instructor/pilot friend is very experienced and very good with dealing with nervous nellies, you will probably learn to relax. I would suggest some touch-and-goes, with your hands on the yoke (with the instructor at first, and then with his hands off, and just yours on it). This will give you a sense of control and ease. Whatever you do, don't go up in a small plane in the back seat with no headphones and with no one to help you calm down if needed. It is cramped, noisy, hard to hear without the intercom/headphones, and if you panic with no one to help you calm down you may start grabbing for the pilot...that would be dangerous to you and to him.
All of this said, I have an old colleague who had a fear of flying, and she overcame it...she had to because of her job (US country manager in a global company with HQ in Europe). I do know that she went for counseling for a very long time, and took Amtrak for cross country trips during the worst of her phobic period. I think she also ended up taking anxiety meds when she finally flew again, and she never flew alone. I flew with her once on a trip from SFO to Boston (she was lightly medicated), and we hit a very minor bit of turbulence and she came a bit unglued...grabbed my hand, and I squeezed it harder than the strongest handshake I have ever had from a big brawny guy...and I'm a guy.
Finally, I would suggest the Fear of Flying program you mentioned. I would not do it this weekend though. Rather, make an appointment way out in advance, get counseling and maybe even meds in the meantime, and go do the program when you can. You've got some time, you're retired. In the meantime, drive.
R